diff --git a/mopidy/outputs/base.py b/mopidy/outputs/base.py
index 372d7d70..ae1af8cf 100644
--- a/mopidy/outputs/base.py
+++ b/mopidy/outputs/base.py
@@ -67,7 +67,7 @@ class BaseOutput(object):
 
         *MUST be implemented by subclass.*
 
-        :rtype: int
+        :rtype: int or :class:`None` if unknown
         """
         raise NotImplementedError
 
diff --git a/mopidy/outputs/dummy.py b/mopidy/outputs/dummy.py
index 060ee02f..e78d269c 100644
--- a/mopidy/outputs/dummy.py
+++ b/mopidy/outputs/dummy.py
@@ -32,7 +32,7 @@ class DummyOutput(BaseOutput):
     end_of_data_stream_called = False
 
     #: For testing. Contains the current position.
-    position = 0
+    position = None
 
     #: For testing. Contains the current state.
     state = 'NULL'